The Department of Health and Human Services’ (HHS) Office of the Inspector General (OIG) issued a report in May 2026 where it reviewed a sampling of 97 enrollees’ diagnoses code submissions from Medicare Advantage Organizations (MAOs) and found that in all cases, the MAOs submissions related to high-risk acute stroke diagnosis codes were unsupported. In this case, a physician data record included the diagnosis but there was no corresponding inpatient or outpatient hospital data with this diagnosis in the same year. Based upon these findings, HHS OIG estimates that the Centers for Medicare and Medicaid Services (CMS) made $462 million in potential net overpayments to these MAOs in 2021 and recommends a procedural change to prevent these overpayments in the future.

This report gives more fuel to the concerns raised by MedPAC and members of Congress about some MAOs upcoding practices, which lead to a higher risk score for a beneficiary and in turn result in higher payments to MAOs. The full report can be read here.